Soft tissue Tumors - Calcifying aponeurotic fibroma

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Soft tissue Tumors

Fibroblastic / myofibroblastic tumors

Calcifying aponeurotic fibroma

Reviewer: Komal Arora, M.D. (see Reviewers page)
Revised: 19 July 2012, last major update July 2012
Copyright: (c) 2003-2012, PathologyOutlines.com, Inc.

Definition
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● Rare, slow growing, painless tumor with fibroblasts palisading around chondroid or calcified nodules, usually in hands and feet of children or young adults; rarely at other sites (Hum Pathol 1998;29:1504)
● Also called juvenile aponeurotic fibroma

Clinical description
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● 50% recur, especially in children
● Does not metastasize
● May be cartilaginous analog of fibromatosis

Treatment
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● Conservative excision with reexcision as necessary for recurrences

Case reports
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● 2 year old child with giant intramuscular calcifying aponeurotic fibroma of gluteus maximus (Ann Trop Paediatr 2010;30:259)
● 10 year old girl with elbow tumor (J Med Invest 2011;58:159)
● 16 year old girl with foot tumor (Case of the Week #47)
● 36 year old woman with distal phalangeal bone involvement (Korean J Radiol 2008;9:91)
● Recurrent tumor of the thumb (J Hand Surg Am 2011;36:110)

Clinical images
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46 year old woman

36 year old woman with distal phalangeal bone involvement

Gross description
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● Nodular or infiltrative gray-white, gritty mass in subcutaneous tissue or tendon, may be calcified, usually 3 cm or less in hands or feet, may be larger elsewhere

Micro description
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● Nodules of plump or epithelioid fibroblasts palisading around cartilage and spotty calcification
● Cells have indistinct and variable cytoplasm, plump oval nuclei with vesicular chromatin that may be condensed below nuclear membrane
● Fibrocytes in stroma between nodules have dense, evenly dispersed chromatin
● May infiltrate fat or striated muscle at periphery
● Frequent osteoclast-like giant cells
● Rare mitotic figures, no atypia
● More cellular in very young

Micro images
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Poorly circumscribed fibroproliferative process with scattered, linear and calcified zones

Amorphous calcification surrounded by palisading cells suggestive of rheumatoid nodule or crystals

Typical zonation pattern has cellular, plump fibroblastic cells palisading
around a hyalinized collagenous zone, which in turn surrounds the calcification

Cells adjacent to hyalinized layer are commonly more rounded

Chondroid area is adjacent to calcification

16 year old girl with foot tumor

36 year old woman with distal phalangeal bone involvement

Cytology description
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● Benign appearing spindle cells, chondroid cells, multinucleated giant cells and calcified debris (Diagn Cytopathol 2001;24:336)

Positive stains
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● Vimentin, CD68, CD99, S100, muscle specific actin (50%), smooth muscle actin (50%)

Negative stains
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● (Usually) CD34, CD57, PR

Electron microscopy description
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● Chondrocytes, fibroblasts and occasional myofibroblasts

Molecular
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● Benign, but may be aneuploid (Cancer 1994;73:1200)

Differential diagnosis
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● Infantile fibromatosis: usually involves head, neck and proximal extremities in infants, not hands and feet of children/young adults, background is more myxoid than chondroid, calcification is rare
● Superficial [palmar and plantar] and desmoid fibromatosis: usually no calcification or chondroid differentiation
● Chondroma of soft parts: may involve hands, but usually well circumscribed with more well developed chondroid differentiation, no infiltration of adjacent tissue, no surrounding epithelioid cells
● Fibrous hamartoma of infancy: immature mesenchyme, fibroblasts are arranged in trabeculae but no palisading, no cartilage or calcification, not hands and feet

Additional references
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● Acta Orthop Belg 2001;67:412, Stanford University

End of Soft Tissue Tumors > Fibroblastic / myofibroblastic tumors > Calcifying aponeurotic fibroma

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